You do not have to metallize the backside of the die to ground it.
Conductive adhesive used in placing the die on a grounded pad will be OK and
the placing action is enough to make an electrical connection through normal
oxide layers to the silver or gold metal particles in the adhesive. The goal
of a connection to ground (or power) is to reverse bias any substrate diodes,
however, if you have an SOI (silicon on insulator) construction on the die
then grounding is not necessary and could perturb your high frequency
characteristics if you used it due to the substrate capacitance.
Hybrid & MCM Consultant
Begin Included Message:
>Subj: [SI-LIST] : backside metal
>Date: 9/10/1999 3:17:05 PM Central Daylight Time
>From: firstname.lastname@example.org (Matt Kaufmann)
>Can anyone comment on the necessity of metallizing the backside of the die
>if we want to ground the backside? In other words, if we want to have an
>electrical connection between the package substrate and the backside of the
>die, is backside metallization required or is the presence of electrically
>conductive adhesive sufficient (assuming the die sits on a grounded die
>Senior Packaging Engineer
>Silicon Spice Inc.
End Included Message.
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